2 Answers
2

Go to Preferences and make sure your audio interface is selected for input. You can select a different interface for input and output, so being able to hear VSTs coming out your interface doesn't ensure that Ableton is configured correctly. Also note that if you start Ableton up with the audio interface unplugged, Ableton will forget about it, and you will have to select it again.

Pick an Audio track, or create a new one

Click the Record button at the bottom of the track - this is the rectangle with a circle in it.

Use the Audio From boxes to select your audio interface and the correct input. If you make some noise into the mic, you should see the meter bounce around in resposne.